1. Field of the Invention
The present invention relates to an arrangement for the production of spherical particles from drops of aqueous solutions of nitrates constituted of uranium, plutonium or thorium, as well as mixtures of these materials for the fuel and breeder elements for nuclear reactors; which consists of a receptacle for an aqueous and a superimposed gaseous ammonia phase, as well as a spray nozzle for producing the drops which is provided with a vibrator and is in communication with a receptacle for the fuel or breeder material solution, wherein the drops traverse the ammonia gas phase under the influence of gravity and also a horizontally-directed force, while traversing the aqueous ammonia phase under only the influence of gravity.
Fuel or breeder material particles of that type are utilized, in a first instance, in the production of fuel and/or breeder elements for high-temperature reactors. Thereby, it is important that the fuel or breeder material particles are obtained in the most possible uniform size and herewith evidence a good spherical shape.
2. Discussion of the Prior Art
In the present state of the technology it is known that such fuel or breeder material particles can be produced in that initially there is formed a nitrate solution from the fuel material or the breeder material, and this solution is thereafter divided into drops, then travels through a gaseous ammonia phase for stabilization and subsequent thereto through a liquid ammonia phase, while a portion of the solidification process is anticipated by addition of ammonia to the fuel and breeder material solution prior to dissipation into drops.
In order to divide the solution of the fuel material or breeder material into drops and to effectuate the solidification; pursuant to a process known from energia nucleare "The SNAM Process for the Preparation of Ceramic Nuclear Fuel Microspheres: Laboratory Studies", April 1970, Issue 4, Volume 17, by G. Brambilla, P. Gerontopulos, D. Neri; spray nozzles are perpendicularly arranged over a precipitation/gelation column formed from a gaseous ammonia phase and a liquid ammonia phase, above which the stream emanating therefrom is divided into individual drops by vibration. Inasmuch as the drops of the fuel or breeder material solution are initially travelling through a gaseous ammonia phase, there is achieved the formation of a shell of sufficient solidity for these drops so as to be able to withstand the impact on the liquid ammonia phase without permanent deformation or even fragmentation. However, in this known arrangement there was encountered the disadvantage that there had to be taken into consideration either extremely large dropping heights, meaning dropping heights of a number of meters, in order to attain the conditions desired in actual practice, or the impact of the drops on the aqueous ammonia phase was so large as to lead to non-uniform and unequally sized particles.
In order to avoid these disadvantages, viscosity increasing substances, such as polyvinyl alcohol, have also been previously added to the fuel or breeder material solution so as to, in this manner, increase the inherent stability of the particles which are to be formed. Nevertheless, it was disadvantageous in this process that this necessitated additional and, consequently, cost-increasing measures in the production of the particles.
Furthermore, also known is a process for the production of fuel and/or breeder material particles in which an injection nozzle is directed from above at an angle of about 10.degree. to 45.degree. towards the surface of an organic liquid located in the receptacle at a small perpendicular distance from the nozzle, and provided for the solidification of the drops formed from the fuel or breeder material solution (German Laid-Open Patent Application No. 2,150,474). Through the angular positioning of the nozzle, and as a result of the low dropping height due to the small distance from the surface of the liquid, there is to be avoided that the drops which are injected from the nozzle will impact with force on the liquid surface. The additionally provided liquid hereby evidenced such a composition that a shell formation for the drops became superfluous prior to the passage into the liquid phase serving for solidification. However, it is disadvantageous, as has been indicated, that in this process there concurrently is not precluded the deformation of the drops, so that the particles formed therefrom are, to a considerable extent, not spherical. A further serious disadvantage is encountered in that, due to the interposition of a liquid preceding the passage into the phase serving for solidification there occurred a recombination of the separated drops, so that the particles produced pursuant to this process, additionally, appeared in considerably different sizes.